Hi! For ranked games, you have 24 hours to take your turn. If you can’t do that, you automatically lose.
For un-ranked games, you have 24 hours to take your turn. Then the opposing player gets an option to send you a notification - for other 24 hours. If you still haven’t taken your turn after that, the opposing player gets an option to kick you out of the game (which will mean your defeat). If there are allied players in your team, they will get control over your nation.